34 morbidly obese patients scheduled for bariatric surgery underwent a preoperative three-week preparation by rapid-weight-loss-diet (RWL) to be accepted for bariatric surgery. Preoperative transthoracic echocardiography (TTE) was performed in the awake state before and after volume-challenge (VC) based on 6ml colloids /kg IBW. Feasibility of standardized VC was evaluated by TTE. Dynamic and non-dynamic echocardiographic indices for VC were studied.